Electrical power networks are liable to cascading outages and blackouts as a consequence of stability problems. Large, widely geographically distributed electrical power networks can, in certain circumstances, be more prone to stability problems, although it should be appreciated that problems can arise in electrical power networks of more modest size. Furthermore the ever increasing use of renewable generation reduces inertia within an electrical power network and thereby increases liability to outages and blackout.
It has long been known to use distributed control approaches to mitigate the consequences of stability problems. Such distributed control approaches involve local control, such as governor-frequency response and under-frequency load shedding, in dependence on local measurements. However such distributed control approaches are becoming too slow to react to electrical power network disturbances or they react disproportionately. Local distributed control involves an inherent delay by setting thresholds that discriminate between local effects and events affecting the wider electrical power network. Furthermore such distributed control approaches are often incapable of operating to advantage with fast acting control apparatus such as more recently developed power electronics.
It is also known to use System Integrity Protection Schemes (SIPS) to mitigate the consequences of stability problems. SIPS comprise a range of protection schemes which are operative to initiate at least one of controlled generation and load tripping in dependence on network faults which would otherwise lead to problems such as loss of synchronism, cascading outages and blackout. SIPS may take the form of relatively simple inter-tripping between network circuits and generators through to taking account of complex logical combinations of events configured for specific operating scenarios. The performance of SIPS is recognised as being mixed. SIPS involve effecting control in dependence on pre-programmed contingencies whereas actual electrical power network disturbances involve complex sequences of events and uncertain dynamic responses. SIPS are therefore liable to respond incorrectly to disturbances under certain circumstances and thereby allow greater problems to develop. SIPS are configured to over-respond to disturbances and thereby incur greater cost. Furthermore over-response may result in the electrical power network experiencing disturbance from the SIPS response in addition to the disturbance from the initial event that gave rise to the SIPS response. A further shortcoming is the centralised nature of SIPS. Centralised systems are liable to single point failure. The deployment of plural SIPS may address the problem of single point failure. However unanticipated interaction between plural SIPS during a disturbance is not unknown.
The present inventors have become appreciative of the above mentioned shortcomings of known approaches to control of an electrical power network with embodiments of the present invention having been devised in light of this appreciation. It is therefore an object of an embodiment of the present invention to provide an improved method of controlling an electrical power network in dependence on a sudden event, such as loss of transmission line, generator or load, which is liable to lead to further loss or excess of generation or load within the electrical power network or part of the electrical power network.
It is a further object of an embodiment of the present invention to provide improved apparatus for controlling an electrical power network in dependence on a sudden event which is liable to lead to further loss or excess of generation or load within the electrical power network or part of the electrical power network.
It is a yet further object of an embodiment of the present invention to provide an improved electrical power network configured for control in dependence on a sudden event which is liable to lead to further loss or excess of generation or load within the electrical power network or part of the electrical power network.